Method and system for controlling the temperature of an indoor space based on wall cavity temperatures

ABSTRACT

A method for controlling a heating system is disclosed. The method comprises obtaining a reading for a temperature of a wall cavity in a structure served by the heating system for an indoor space adjacent to the wall cavity, determining an equivalent wall cavity temperature (ET), and when ET is less than or equal to a threshold temperature (TT), selecting a chosen set point by selecting a default set point (DS). When ET is less than TT, the method comprises determining a calculated set point (CS) based on the ET, comparing the CS to the DS and a maximum set point (MS) and selecting the chosen set point by selecting DS if CS is the DS, CS if CS is between DS and MS, MS if CS is above MS; and controlling the heating system to regulate the temperature of the indoor space according to the chosen set point.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 62/146,288 filed Apr. 11, 2015, entitled “SYSTEM AND METHOD FOR CONTROLLING THE TEMPERATURE INSIDE A BUILDING BASED ON THE TEMPERATURE OUTSIDE THE BUILDING” which is incorporated herein by reference in its entirety.

BACKGROUND

1. Field

This disclosure relates to heating control systems, and methods for controlling heating systems. More particularly, the disclosure describes heating control systems, and methods of controlling heating systems, which use wall cavity temperature information to achieve energy savings.

2. Description of Related Art

Thermostats and Temperature Control Systems

Conventional temperature control systems often use thermostats to allow the user to create predetermined set points for indoor temperatures. A thermostat samples the temperature within a structure, and calls for heat or cooling from a heating, cooling, or HVAC system. Thermostats are used with all manner of heating, cooling and HVAC systems; and the settings on the thermostat are usually driven by considerations for the comfort or safety of the occupants of the structure. The temperature in a structure can be managed by one or more temperature control system, and by one or more heating, cooling or HVAC system. Either or both of the temperature control system or heating control system can be stand-alone, or can be a part of a building management system.

Current thermostats can be programmable to allow set points to be programmed for specific times of day, and for days of week. These times and set points can correspond to, for example, when the user expects the building to be occupied, when the occupants are expected to be away such as during the workday, or when the occupants are typically asleep.

More recently-developed thermostats can regulate energy usage in response to peak demands on the power grid. Such thermostats call for, for example, less cooling in a structure when the power grid is at peak usage, and some thermostats of this type are also able to sense whether a structure is occupied, and even further reduce power consumption during times of peak demand if the structure is unoccupied.

Other recently-developed thermostats use the future occupancy status of the structure to determine set points for the temperature of the space. For example, a thermostat can receive a signal via the internet indicating that an occupant will soon arrive at the structure, and adjust its temperature set point accordingly. In other cases, based on historical data regarding occupants' movement in the structure, a thermostat can predict when the structure will be occupied, and adjust its temperature set point accordingly. For structures which are regularly occupied, these technologies, alone or in combination, are both energy efficient and ensure optimal comfort of an occupant of the structure.

Unoccupied Structures

None of the above-described thermostat functionalities, however, addresses the need for energy-efficient heating of unoccupied structures. According to the U.S. Census Bureau estimates, there were approximately 17.3 million vacant housing units in the United States as of the first quarter of 2015.

In colder climates throughout the world, such unoccupied structures are unnecessarily heated in order to prevent damage to the structure from cold, in particular from freezing pipes. Second homes, vacation homes, offices, any structures left unoccupied for extended periods, and even particular zones within a structure that are expected to have longer periods of time where they are unoccupied, can benefit from a system which will heat the space within the structure enough to prevent damage from cold, without unnecessarily heating the space. In these situations, the comfort of an occupant is not the objective; rather, a combination of energy savings and prevention of damage to the structure caused by the temperature is. Currently, the temperature in such unoccupied structures is usually set to a single pre-selected set point, and the space within the structure is kept consistently at that temperature. In colder climates, this pre-selected set point is selected because it will keep the space within the structure warm enough to prevent damage to the structure from cold, for example from freezing pipes. A typical fixed setting of 50-65 degrees Fahrenheit is often selected for such situations. (The lowest recommended setting, per the American Red Cross, as well as major insurance companies and others, is to 55 degrees Fahrenheit while buildings are unoccupied.) Such a setting is high enough to keep the unoccupied structure safe during periods of extremely low temperatures, when there is a risk of damage to the structure, for example from freezing pipes. Decreasing the indoor temperature from 68 degrees Fahrenheit to 55 degrees Fahrenheit (a difference of 13 degrees Fahrenheit) produces estimated savings of 39% in these unoccupied structures. (The U.S. Department of Energy estimates up to 1% savings on heating for each 1 degree Fahrenheit of setback for an eight hour period. Estimating savings for unoccupied spaces over a whole day would therefore mean 24 hours per day savings or 3% savings per 1 degree setback.)

In times of only moderately low temperatures, however, for example, when outdoor temperatures are 35-50 degrees Fahrenheit, a thermostat setting of 55 degrees Fahrenheit causes heating of the unoccupied structure which is not necessary to prevent damage. A further 15-20 degree reduction in indoor temperature set point (from 55 to 40 or 35 degrees Fahrenheit) could yield significant savings: approximately 45-60% of the estimated energy currently being expended to heat unoccupied homes. Therefore, a vast amount of energy is wasted worldwide. On most days, structures that are expected to be unoccupied for longer periods are kept much warmer than would be necessary to prevent plumbing and property damage.

In many unoccupied structures, the default temperature setting, and therefore the amount of energy used to heat the space, could be dramatically lowered if the heating control system in the structure could reliably and automatically call for heat only when the chance of damage from frozen pipes increases.

Structural Design

In many structures, pipes are located in a wall cavity. In other words, a structure's pipes are not located fully in the interior space of the structure. Therefore, the pipes experience a different atmosphere in the structure's wall cavity than that in the interior space of the structure. Specifically, the temperature in the wall cavity is, or approaches, an average of the temperature of the indoor space of the structure and the temperature outside the structure. Of course, the temperature in the wall cavity can be influenced by many factors, including but not limited to, the presence and location of insulation, whether the outside wall is heated by sunlight at a given time, whether the outdoor wall is exposed to wind, etc.

This design feature of some structures, then, creates an additional challenge in preventing damage to the structure in times of colder temperatures. The recommended settings by the American Red Cross and others, of a thermostat setting of 55 degrees Fahrenheit, are an attempt to blindly compensate for difference in the temperature in the wall cavity (where the pipes reside), and the temperature in the indoor space of a structure. Ideally, a heating control system could more accurately determine the actual temperature required in the indoor space, which is required to prevent freezing pipes in the wall cavity.

Currently, heating control systems are not available with this functionality. There therefore remains a significant need for a method of controlling the heating of a structure which considers wall cavity temperature and provides enough heating to the indoor space to prevent damage to the structure from cold, but without expending unnecessary energy.

SUMMARY

The present disclosure provides a method for controlling a heating system. The method can include obtaining a reading for a temperature of a wall cavity in a structure served by a heating system which heats an indoor space adjacent to the wall cavity and determining an equivalent wall cavity temperature (ET) based on the obtained reading. When the equivalent wall cavity temperature is at or above a threshold temperature (TT); a chosen set point is selected by selecting a default set point (DS). When the equivalent wall cavity temperature is below the threshold temperature, the method can include determining a calculated set point (CS) based on the equivalent temperature (ET). A calculated set point can be based on the difference between the threshold temperature and equivalent temperature (DIFF), and it can be further based on whether this difference is increasing or decreasing over time. The method can include comparing the CS to the DS and a maximum set point (MS) and selecting a chosen set point by selecting (1) the DS if the CS is below the DS, (2) the CS, if the CS is between the DS and the MS, or (3) the MS, if the CS is above the MS. The method can further include controlling the heating system to regulate the temperature of the indoor space according to the chosen set point.

In controlling the heating system, when the calculated set point is above the maximum set point, the method can display to the user that the maximum set point is in use, it can further notify the user of the same information. Likewise, the DIFF can be displayed and the user can be notified of the DIFF. If an equivalent wall cavity temperature cannot be determined, a fail-safe set point is chosen and the indoor temperature is managed by the heating control system to this temperature, the system can display this status, and the user can be notified accordingly.

Alternatively, the method can include obtaining a reading for a temperature of a wall cavity in a structure served by a heating system which heats an indoor space adjacent to the wall cavity, and determining an equivalent wall cavity temperature (ET) based on the obtained reading. When the equivalent wall cavity temperature is at or above a threshold temperature (TT); a chosen set point is selected by selecting a default set point (DS). When the equivalent wall cavity temperature is below the threshold temperature, the method can include comparing the indoor temperature to a maximum allowable temperature and controlling the heating system to increase the indoor temperature until either 1) the equivalent wall cavity temperature is at or above the threshold temperature, i.e. DIFF is 0 or negative, or 2) the indoor temperature is at or above the maximum allowable temperature. When either of these conditions is met, the method discontinues calling for heat from the heating system.

In controlling the heating system, when the indoor temperature (IT) is at or above the maximum allowable temperature (MT), the method can display to the user that the IT has reached the MT , it can further notify the user of the same information. Likewise, the DIFF can be displayed and the user can also be notified of the DIFF. If an equivalent wall cavity temperature cannot be determined, a fail-safe set point is chosen and the indoor temperature is managed by the heating control system to this temperature. In this case, the system can display this status, and the user can be notified accordingly.

The present disclosure further provides a heating control system. The heating control system can include at least one user interface. The heating control system can include at least one computer. The computer can be programmed to obtain a reading for a temperature of a wall cavity in a structure served by a heating system which heats an indoor space adjacent to the wall cavity and determining an equivalent wall cavity temperature (ET) based on the obtained reading. When the equivalent wall cavity temperature is at or above a threshold temperature (TT); a chosen set point is selected by selecting a default set point (DS). When the equivalent wall cavity temperature is below the threshold temperature, the heating control system can determine a calculated set point (CS) based on the equivalent temperature (ET). A calculated set point can be based on the difference between the threshold temperature and equivalent temperature (DIFF), and it can be further based on whether this difference is increasing or decreasing over time. The system can compare the CS to the DS and a maximum set point (MS) and select a chosen set point by selecting (1) the DS if the CS is below the DS, (2) the CS, if the CS is between the DS and the MS, or (3) the MS, if the CS is above the MS. The heating control system can further control the heating system to regulate the temperature of the indoor space according to the chosen set point.

When the calculated set point is above the maximum set point, the heating control system can display to the user that the maximum set point is in use, it can further notify the user of the same information. Likewise, the DIFF can be displayed and the user can be notified of the DIFF. If an equivalent wall cavity temperature cannot be determined, the heating control system chooses the fail-safe set point and the indoor temperature is managed by the system to this temperature. The system can display this status, and the user can be notified accordingly.

Alternatively, the heating control system can obtain a reading for a temperature of a wall cavity in a structure served by a heating system which heats an indoor space adjacent to the wall cavity, and determine an equivalent wall cavity temperature (ET) based on the obtained reading. When the equivalent wall cavity temperature is at or above a threshold temperature (TT); the system can choose a set point by selecting a default set point (DS). When the equivalent wall cavity temperature is below the threshold temperature, the system can compare the indoor temperature to a maximum allowable temperature and control the heating system, to increase the indoor temperature until either 1) the equivalent wall cavity temperature is at or above the threshold temperature, i.e. DIFF is 0 or negative, or 2) the indoor temperature is at or above the maximum allowable temperature. When either of these conditions is met, the heating control system discontinues calling for heat from the heating system.

When the indoor temperature (IT) is at or above the maximum allowable temperature (MT), the heating control system can display to the user that the IT has reached the MT, and it can further notify the user of the same information. Likewise, the system can display the DIFF and notify the user of the DIFF. If an equivalent wall cavity temperature cannot be determined, the heating control system can choose the fail-safe set point and manage the indoor temperature to this temperature. The system can display this status, and the user can be notified accordingly.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive body of work will be readily understood by referring to the following detailed description in conjunction with the accompanying drawings, and as set out in the appended claims.

FIG. 1 is a diagram showing the overall operation of the system and method disclosed herein.

FIG. 2 is a diagram showing a possible configuration for a user interface screen for the method.

FIG. 3 is a flow diagram showing an exemplary functional logic which the heating control system can employ.

FIG. 4 is a flow diagram showing an alternative exemplary functional logic which the heating control system can employ.

FIG. 5 shows a conventional fixed setback using a set point of 55° F. that is not impacted by changes in outdoor temperature. In contrast, an example is shown of the indoor temperatures that can result from utilizing one embodiment of the present technology, and how indoor temperature can change in relation to outdoor temperature.

FIG. 6 shows a comparison of estimated relative costs for three different fixed thermostat settings. Costs are based on the US Department of Energy's approximation for savings achieved by turning down a thermostat during the heating season.

DETAILED DESCRIPTION

In colder climates, the freezing and subsequent bursting of pipes can be a significant problem. In an occupied structure, such as a home or office, the space within the structure is usually heated sufficiently to keep the occupants of the structure comfortable. Temperatures that are high enough to keep the occupants of a structure comfortable, for example, a temperature at or above 65 degrees Fahrenheit, are usually sufficient to prevent damage to the structure due to cold, for example, to prevent the pipes within the structure from freezing.

In unoccupied structures, however, for example in homes in which no one is resident, or in unoccupied commercial or storage structures, the temperature is usually kept at a fixed point, and left for the duration of the time that the structure remains unoccupied. The reason for this action is to prevent damage from extremely low temperatures inside the structure; specifically, to prevent the freezing of water in, and subsequent bursting of, pipes. A reasonable set point for an unoccupied structure using a standard heating control system is often between about 50-65 degrees Fahrenheit. Such a set point means that when outdoor temperatures are at or above about 32 degrees Fahrenheit, but the temperature inside the structure is below 50-65 degree Fahrenheit, the heating control system continues to call for heat even though it is not needed to prevent the structure's pipes from freezing. Such an arrangement can result in a significant amount of unnecessary heating, and consequently of unnecessary energy use, and resulting greenhouse gas emissions.

The method and system disclosed herein cause increases in the indoor temperature of a structure in an inverse relationship to the outdoor temperature during periods of colder weather, for example, when there is a danger of damage to the indoor space from cold weather. Specifically, the system and method disclosed herein concern themselves with the temperature in a wall cavity of an unoccupied structure, and in regulating the temperature in the wall cavity to prevent freezing pipes by controlling the indoor temperature.

A structure comprises indoor space, or simply “space,” in which objects, animals or people can be disposed. The indoor space is separated from outdoor space by one or more walls. As used herein, the term “wall” does not require that the wall extend vertically or substantially vertically. Rather, walls can extend horizontally or substantially horizontally, such as in the case of a floor or a ceiling; or walls can extend neither vertically nor horizontally, such as a pitched roof.

Most, but not all, structures have two sets of walls between the indoor space and the outside space: an interior wall and an exterior wall. The interior walls, ie, those defining the inside space, can be made of wallboard, wood, or any other suitable material. The exterior walls face outward (i.e., outdoors) and can be made of wood, brick, concrete, cinder block, or any other suitable material. In some cases, an exterior wall can be covered with an additional covering; for example, a wooden exterior wall can be covered with vinyl or metal siding on its exterior face, and may have at least one of a vapor barrier and layer of insulation between the exterior wall and the additional covering.

An interior wall and an exterior wall together define an exterior wall cavity. The wall cavity is the space between the external face of the interior wall and the internal face of the exterior wall. An interior wall cavity is defined by two interior walls, for example between two walls of a structure which create a wall dividing two spaces inside the structure. Both an interior wall cavity and an exterior wall cavity can comprise any or all of air, insulation, pipes, wiring, ductwork, piping for a heating system, or other buliding infrastructure.

In many cases, and especially in residential structures, the structure's pipes are housed in wall cavities, for example, in exterior wall cavities. Pipes that are located in exterior wall cavities are especially prone to freezing and subsequent bursting when outdoor temperatures fall below freezing. Pipes can additionally or alternatively be located within an interior wall cavity where the risk of freezing is lower than in an external wall cavity. However, it is not uncommon for pipes to be located in exterior wall cavities; such pipes, and specifically the water they comprise, need to be kept at temperatures above freezing to avoid burst pipes and resultant property damage.

The temperature inside an external wall cavity is generally determined by both the outdoor temperature and the indoor temperature. The actual temperature of a wall cavity, whether an exterior cavity or an indoor cavity, is determined by the materials which define the wall cavity, the location of the wall cavity (eg, interior or exterior, in the sun or not, facing north or south), insulating capacities and positioning of such insulation and building materials.

The method described herein can be used to control the temperature in any suitable indoor space. A suitable indoor space, as used herein, has at least one pipe in a wall cavity. Suitable indoor spaces include, but are not limited to, a residence, a commercial building, and a moveable space. A residence can be, but is not limited to, one or more of a detached home and a multi-family residential dwelling. A multi-family residential dwelling can be, but is not limited to, one or more of a duplex, a semi-detached home, a townhouse, an apartment, a condominium and a co-op. A commercial building can be, but is not limited to, one or more of an office space, an office building, a retail space, an industrial building and a storage building. A moveable indoor space can be, but is not limited to, one or more of a train wagon, a ship, a boat, an airplane, a recreational vehicle and a mobile home.

In one embodiment, the system can be configured to function in a vacant building, for example one which can be for sale or rent, and which does not have wireless Internet service. In these circumstances, it is anticipated that remote communication with the system can be accomplished through a cellular telephone network or other wireless technology, either directly with the heating control system, or via a separate apparatus within the building and in proximity to the heating control system, and communicating with the heating control system either through a wired connection, or through a wireless method or via a thermal interface. The cost of such a simple configuration is anticipated to be modest in comparison to the energy savings to be realized by implementing the present invention.

The method can be implemented on an apparatus (a heating control system; eg, a thermostat) already resident in the structure, or can be implemented by one or more heating control system designed specifically to implement the method. The present disclosure provides a method for providing sufficient heat to a structure to prevent damage from cold temperatures or freezing pipes, while decreasing the overall energy usage of the structure.

Structures are heated or cooled by heating or cooling systems, respectively; and can be both heated and cooled by an integrated heating and cooling system such as a HVAC (heating, ventilation and air conditioning) system. The present technology concerns itself with heating an indoor space, and therefore with a heating system or the heating component of an HVAC system. A heating system comprises at least one heating mechanism (for example, a furnace) as well as a way to heat directly, such as electric resistance heat, or moving a heated fluid such as air or water through the structure. A heating system can be a heat-only system, or, for the purposes of this disclosure, the heating components of an HVAC system, either of both which meanings, as well as equivalents thereof, are encompassed by the use of “heating system” herein.

The methods and systems disclosed herein can be used with any type of heating system. The heating system can be a heat-only system. The heating system can be a heating, ventilation and air conditioning (HVAC) system. The heating system can be a forced-air system. The heating system can be a radiant heating system. The radiant heating system can comprise one or more of electric resistance heat elements, traditional radiators, under-floor heating elements, and behind-wall heating elements. The heating system can produce heat in any way known to those skilled in the art. The heating system can, for example, use electricity, or burn fuels such as natural gas, LP, propane or fuel oil.

A heating system comprises at least a furnace and a furnace control system. As used herein, the term furnace is a generic term encompassing the heating element of all types of heating systems. “Furnace,” as used herein, includes but is not limited to a furnace, a boiler, a heat pump, an electrical resistance heater, a geothermal based system, a solar system, a wood-burning heater, a fossil fuel-burning heater, and other types of heating systems.

Furnaces are activated by a furnace control system. The furnace control system can receive signals from a heating control system. The heating control system is usually, though not always, separate from the furnace control system. The heating control system can be connected to the furnace control system by wired circuits, wireless apparatus, optical fibers, or any other method that allows signaling to call for heat.

A heating system can be controlled by a heating control system. Generally, heating control systems provide a way for a heating system to respond to user requirements for an indoor space to be maintained at a particular temperature. Heating control systems can comprise at least one thermostat. The thermostat can read the temperature in the indoor space in which it is installed, compare that temperature to a pre-selected set point, and then, optionally, relay the need for heating to the furnace control system. The furnace can then provide heat until the thermostat reads the temperature in the indoor space as equal to, or within a pre-selected range of, the set point.

In one embodiment, the methods described herein are implemented on, by, or in conjunction with a heating control system. The heating control system can be co-located with the structure requiring heating, or can control the heating system at the structure from a different physical location. In the case that the heating control system controls the heating system from a different physical location, the heating control system and the heating system can be in communication through any method, including but not limited to electronic communication such as a wired or wireless internet connection, satellite, cellular telephone or standard telephone network.

In general, the present disclosure provides a method for controlling a heating system. Controlling the heating system of an indoor space can comprise controlling the furnace control system to determine the temperature to which the indoor space serviced by the heating system is managed. Control of the heating system can be accomplished by positive control or negative control. In the case of positive control, controlling involves either calling for heat or selecting a predetermined set point managed by the furnace control system. Negative control is prevention of the normal operation of the furnace control system (calling for heat). The heating control system can be directly connected to the furnace control system. Alternatively, the heating control system can communicate with the furnace control system through an existing temperature control apparatus such as a thermostat.

In one embodiment, a heating control system can be connected to an existing temperature control apparatus through a thermal interface. The thermal interface can produce heat, causing the temperature measuring devices of the existing temperature control apparatus to register a higher temperature than the ambient temperature of the space, thereby preventing the activation of the furnace control system that would otherwise occur. This is an example of negative control.

To keep an external wall cavity sufficiently warm to prevent the freezing of water in any pipes located therein, the temperature inside the adjacent indoor space can be increased. The method disclosed herein can comprise obtaining a reading for a temperature of a wall cavity in a structure served by a heating system which heats an indoor space adjacent to the wall cavity. A reading of wall cavity temperature can be the actual temperature in the wall cavity (ie, the reading is obtained by a device located inside the wall cavity), or can be an approximation of the temperature of concealed wall spaces where plumbing is thought to exist in the structure. For example, an approximation of a wall cavity temperature reading can be obtained by using the indoor temperature reading in combination with a reading from the interior face of the interior wall, by contact or optically, and estimating the wall cavity temperature using these two pieces of information. The wall cavity can be an exterior wall cavity.

Wall cavity temperature data can be provided directly to the heating control system, electronically via a network, such as a LAN network, a WAN network, the Internet (either wired or wirelessly), by Bluetooth, satellite, cellular phone network, standard telephone service, a wireless mesh network, or by any combination of these methods.

Once obtained, the reading for wall cavity temperature (WT) can be used to determine an equivalent wall cavity temperature (ET). If there is only one reading for WT, then ET can be WT.

In one embodiment, when there is a plurality of readings for WT, ET can be the lowest (ie, coldest) of the WT readings. Alternatively, ET may be arrived at by averaging the readings for WT, or ET may be arrived at by any other reasonable method which will represent the temperatures where concealed pipes are thought to exist that will be most impacted by outdoor temperatures for the particular installed location.

In one embodiment, a wall cavity threshold temperature (TT) can be determined, either pre-determined or set by the user of the system, which represents the temperature below which the ET should not fall without triggering the heating control system to determine a calculated set point (CS). The calculated set point is the target indoor temperature to which the structure can be heated. The calculated set point is subject to a minimum, i.e. the default set point, and the maximum set point.

TT can be a reference value used in determining if the default temperature can be chosen as the set point. When ET is above TT and outdoor temperature is above freezing, the default set point can be considered adequate to protect the plumbing in wall cavities from damage from low temperatures. During these times, significant amounts of energy can be saved by utilizing the default temperature set point, as compared to systems that use a conventional fixed setting that does not adjust based on WT.

When ET is at or above TT, the heating control system does not call for heat from the heating system unless the indoor temperature (IT) falls below the default set point (DS). The lower TT is set, the greater the energy savings that the system and method deliver to the user. It is possible to prudently set TT to a very low temperature, even below freezing, when pipes are known to be better insulated (ie, warmer) than where temperature readings are obtained, not in wall cavities located on exterior walls or in any wall system thought to be better protected from cold outdoor temperatures.

For purposes of this disclosure, the term “Equivalent Differential” (DIFF) is used to denote the difference between the threshold wall cavity temperature (TT) and the equivalent wall cavity temperature (ET). Or mathematically stated, DIFF=TT−ET

When ET is below TT, DIFF is positive and the heating control system can determine a calculated set point (CS) based on DIFF, which is directly dependent on the readings for wall cavity temperature (WT). When the indoor temperature (IT) reaches CS, like any heating control system, the system ceases calling for heat.

Determining CS can be done mathematically, by performing a set of logical steps, or as a combination of these methods.

In one embodiment, the heating control system can work in a rudimentary fashion, turning on the heat when ET falls below TT and turning it off again when ET is at or above TT. When operating in this mode, the determination of calculated set points is essentially bypassed. Therefore, the system will call for heat until DIFF is less than or equal to 0, or until IT reaches a maximum allowable temperature (MT). At that point, the heating control system discontinues calling for heat from the heating system.

In one embodiment, the heating control system can do one or more of the following: 1) display on the user interface that IT has reached the MT, 2) notify the user that the IT has reached the MT, 3) display on the user interface the DIFF, and, optionally, 4) notify the user of the DIFF.

The calculated set point (CS) can be an integer, or a real number having one or more decimal places.

The (CS) can be compared to a default set point (DS). The DS can be any temperature close to freezing, but which has been determined by the user to be a temperature at which the structure and/or its contents will not be damaged. When protecting against damage caused by the freezing of water, such as water standing in pipes, preferably, the DS is one, two, three, four or five degrees above freezing, or 33, 34, 35, 36 or 37 degrees Fahrenheit; or from six to ten degrees above freezing, or 38, 39, 40, 41, or 42 degrees Fahrenheit.

In one embodiment, when ET cannot be determined, the system selects a fail-safe set point.

The default set point (DS) is the lowest set point to which, when the method is being used, the heating control system can be set.

The calculated set point (CS) can be compared to a maximum set point (MS). The maximum set point (MS) is the highest set point to which, when the method is being used with one or more CS, the heating control system can be set.

A chosen set point can be selected. The chosen set point is the point to which the heating control system controls the heating system to provide heat the indoor space. The chosen set point is selected by selecting one of: (1) the DS if the CS is below the DS; (2) the CS, if the CS is between the DS and the MS; or (3) the MS, if the CS is above the MS.

One or more of the DS, MS, maximum allowable temperature, and TT, can be set at a point in time prior to the WT being obtained, or can be set at a point in time subsequent to the WT being obtained.

When an equivalent wall cavity temperature (ET) is not available (320), a fail-safe set point (F) can be selected (325). F can be set prior to practicing any or all other steps of the method, or at any point during the practice of the method. F can be set by the user at the time of failure of one or more of the steps of the method. A heating control system implementing the method can advise a user of the heating control system that F needs to be set. A heating control system can advise a user of the heating control system that the fail-safe set point has been engaged. F can be in the range of 40-65 degrees Fahrenheit, or it can be any other specific temperature setting which the user defines. A different F can also be set for each month or even week of a heating season. For example, when choosing a F for an indoor space in Alexandria, Virginia, one can choose a higher F such as 60 degrees for the colder winter months of December, January, and February, but choose lower F for November and March such as 50 degrees, and possibly even lower F for October and April such as 45 degrees.

The present disclosure provides a heating control system. The heating control system can comprise at least one user interface, and at least one computer programmed to implement the steps of the method disclosed herein. The user interface can allow a user to program the heating control system, including but not limited to programming at least one of a F, a DS, a MS, a maximum allowable temperature, and a TT. The computer can be a general purpose computer; or it can be a specific purpose computer, programmed specifically to implement the steps of the disclosed method. The computer can store one or more of a user input, one or more WT readings, one or more ETs, in a non-transitory medium. The computer that performs the operations of the method can comprise a general purpose computer, and can also utilize application specific integrated circuits (ASIC), field programmable logic arrays (FPGA), or any other implementation to perform all or part of the method.

The exact mathematical or logical function for CS and the particular values chosen for the parameters, while important for optimizing savings for a particular individual site and application, have only a minor impact on the overall results of the method. Regardless of the exact function used, substantially the same protective benefits and energy savings will be produced. The method, and any apparatus using the method in conjunction with a heating system, will realize the majority of the energy savings by enabling the use of a deep set back temperature, referred to herein as the DS, across a wide range of weather conditions prevalent during the heating season in many geographic regions, because the automatic adjustment feature will engage to provide the protection needed.

In one embodiment, the heating control system can work in a rudimentary fashion, turning on the heat when the ET falls below a TT and turning it off again when the ET is at or above the TT. When operating in this mode, the determination of calculated set points is essentially bypassed. Therefore, the system will call for heat until the DIFF is less than or equal to 0, or until the IT reaches a maximum allowable temperature (MT). At that point, the heating control system discontinues calling for heat from the heating system. The following example will help to illustrate this embodiment.

Due to the physical barriers (eg, indoor walls) between indoor spaces and wall cavities, there can be a lag between changes in IT and ET. To reduce the incidence of unnecessary use of energy, as the DIFF begins to decline, the system can begin to reduce the MG, and therefore the CS.

The heating control system can take into consideration the direction of changes to DIFF. For example, when a DIFF that had been 3 drops to 2, the system can determine a new CS as IT+0, thereby holding the CS steady until the next change in DIFF is logged. If the DIFF continues to decrease, then the system can continue to hold the CS steady until DIFF=0. If DIFF levels off, but is still positive, then CS can be calculated with smaller margins, 1 or 2 for example, thereby increasing IT very slowly, decreasing DIFF to zero without expending unnecessary extra energy to reach the DIFF=0 target. When DIFF is less than zero, then the default set point (DS) will be chosen and heat will not be called for by the heating control system until the IT falls below DS.

Turning now to the figures.

FIG. 1 shows a representative schematic of a structure in which the disclosed system and method can be used, including non-limiting placement of the elements of the system in physical space.

A heating control system (108) can control a heating system. The heating system can comprise a furnace (111) and a furnace control system (110), as defined herein.

The heating control system (108) can interact with a WT sensor (114) used to measure the temperature of a wall cavity (103). The heating control system utilizes this information in determining whether to call for heat from the heating system for the protection of infrastructure in the non-indoor spaces indirectly heated by the heating system. The wall cavity sensor can be placed in the wall cavity, in contact with the inner wall, or using, for example, optical temperature measurement, some distance from the wall adjacent to the wall cavity, or by any other means that allows for a measurement or estimation of the WT.

The heating control system (108) can interact with one or more wide area network (WAN) connections (104), either via a building network (105) as shown, or directly. The heating control system (108) can interact with a temperature sensor (109), which itself can interact with a thermal interface (112). The heating control system (108) can interact with an ambient temperature sensor (113) which measures indoor temperature (IT). The connection to the Internet (105, 104, 102, 101) allows for the user interface device(s) (100) to interact with the heating control system. It also allows for the use of external computers in executing the method.

The heating system can be located in the same indoor section of the structure, or it can be located in a different location in the structure from the heating control system (108).

The heating control system (108) can optionally include an apparatus that controls the existing temperature control system through its temperature sensor (109). This can be accomplished by controlling the apparent temperature the existing temperature control system reads from the original temperature sensor. A thermal interface (112) can generate heat in proximity to the original temperature sensor (109) and the apparatus can thereby control the actual ambient temperature through the use of the set point of the original temperature control system. In this embodiment, the apparatus can use an additional temperature sensor (113) to measure the actual temperature of the indoor space (106) without being impacted by the heat generated by the thermal interface.

For example, when a constant 55 degree set point is set for an existing temperature control system, the heating control system of the present invention, using a thermal interface (112), can provide heat to the original temperature sensor (109) resulting in that sensor, and thereby the existing temperature control system, to read an apparent temperature above 55 degrees. The existing temperature control system would thereby refrain from calling for heat. In this example, the heating control system of the present invention effectively controls the ambient temperature by deceiving the existing temperature control system. In one embodiment where the existing temperature control system is a thermostat, the method and system of the present invention can be employed by adding the heating control system and a simple accessory apparatus, a thermal interface, and without replacing the installed thermostat. This embodiment can enable simplified and low cost implementation of the heating control system of the present invention in situations where replacing a thermostat is an undesirable option such as when a building is for sale or rent and is planned to be vacant for a short period of time.

FIG. 2 illustrates a non-limiting example of a user interface screen (200). The current indoor temperature IT is displayed (202) along with the outdoor temperature (203). Across the bottom are icons showing the current setting for MS or maximum allowed temperature (204), F (205), the selected TT (206), wall cavity equivalent temperature (207), and DIFF (208). Also shown is the DS (209), and the chosen set point (201).

FIG. 3 shows the general method disclosed herein, which a system of the present disclosure can implement. As a general first step, a system can obtain or attempt to obtain a reading for a WT (305). The reading can be obtained from a wall cavity in the structure served by the heating system which heats the indoor space adjacent to the wall cavity. Using the WT reading, the system determines (310) an equivalent wall cavity temperature (ET). It is then determined if the ET is available (320). If the ET is not available, a fail-safe set point is selected (325). The fail-safe set point (F) is any set point for a heating control system which the user believes can adequately protect a structure against damage from any cold temperature without automatic changes to indoor set points. If the ET is available and is at or above (330) the threshold temperature (TT), the DS is selected (335). The DS can be pre-set or is any set point which the user defines, and which is low enough to achieve energy savings as compared to systems which use standard fixed set points, for example 50-65 degrees, for unoccupied structures. The use of this relatively low DS is made possible due to the automatic adjustment to set point when colder WTs occur. If the ET is lower than the TT, then the calculated set point (CS) is determined based on ET (340) and compared (350) to the DS, which essentially serves as the minimum set point, as well as a maximum set point (MS), above which the set point will not be permitted. The DS is chosen (335) if the CS is less than the DS. The CS is chosen (375) if it is between the DS and the MS. The CS is compared to the MS (363) and the MS is chosen (365) if the CS is above the MS. The heating control system controls the heating system to regulate the temperature of the indoor space to the chosen set point.

The general logic of a method for controlling a heating system, and which can be implemented on a heating control system, is shown in FIG. 3. One skilled in the art will recognize that, once the reading for WT is obtained, the order of the logical steps can be altered somewhat, while achieving substantially the same result.

FIG. 4 shows alternative logic for the general method disclosed herein, and which a system of the present disclosure can implement. As a general first step, a system can obtain a reading for a WT (305). The reading can be obtained from a wall cavity in the structure served by the heating system which heats the indoor space adjacent to the wall cavity. Using the WT reading, the system determines (310) an equivalent wall cavity temperature (ET). It is then determined if the ET is available (320). If the ET is not available, a fail-safe set point is selected (325). If the ET is available and is at or above (330) the threshold temperature (TT), the DS is selected (335). If the ET is lower than the TT, then the indoor temperature (IT) is compared to the maximum allowable temperature (MT) as a preliminary step (354) to determine if more heat should be called for. If IT>=MT (355), the system will discontinue calling for heat (356). If IT is not>=MT, then the heating system is controlled to increase IT (357). The MT is any IT which is expected to be adequately warm enough to prevent damage to the structure or its contents, including plumbing pipes, from freezing weather. Similar to MS, MT can limit the heating control system from calling for heat above this point.

FIG. 5 shows a conventional fixed setback (620) using a set point of 55° F. In contrast, an example of ITs that may result (630) from utilizing one embodiment of the present invention is shown. When outdoor temperatures are above about freezing, the default setting is chosen, in this case with a set point of 36° F. In this example, the IT is shown increasing by about 1° F. for each degree the outdoor temperature decreases below about freezing. This graph is a fair approximation since the WT is a function of both indoor and outdoor temperatures, with a general bias toward the IT due to the lower insulation value of the interior side of exterior wall cavities. In this example, at all times when outdoor temperatures are above 9 degrees, energy will be saved over the use of a conventional fixed setback of 55° F. In this illustration, 9 degrees is the breakeven point (610); only when outdoor temperatures decline below 9° will the present invention use more energy to protect the wall cavity from freezing than a conventional fixed setback scheme of 55 degrees.

FIG. 6 shows a comparison of relative costs for three different fixed heating control system settings. These costs are based on the US Department of Energy's approximation for savings achieved by turning down a heating control system during the heating season. The first bar (700), is the base case. It considers as full cost, the energy needed to heat a home to 68°. The next bar (710), reflects 39% savings by setting the thermostat to a fixed setting of 55° for 24 hours per day. The cost of heating, in this example, is estimated to be 61% of the base case. During times (720) when the heating control system chooses the DS, i.e. is set back to 36° for example, it is estimated that the energy cost could be reduced to 26% of the original.

EXAMPLE 1

Parameters:

TT=threshold temperature ET=equivalent wall cavity temperature

DIFF=TT−ET

DS=default set point (serves as default and minimum set point) MS=maximum set point FS=fail-safe set point CS=calculated set point IT=indoor temperature MG=margin used to calculate new set point

CS=IT+MG

When the ET is below the TT, DIFF is positive and the heating control system can determine a calculated set point (CS) based on DIFF, which is based on ET, which is determined from the reading for wall cavity temperature. When the indoor temperature (IT) reaches the CS, like any heating control system, the present system can cease calling for heat.

In one non-limiting example, when TT is 38, outdoor temperature is 22, IT is 47, and ET is determined to be 37, then DIFF is 1. The system can determine a CS to begin to intervene and begin to warm the indoor space. CS can, for example, be IT plus a small margin (MG) appropriate for a DIFF of 1, for example, MG can be 1, 2, 3, 4, or 5 degrees Fahrenheit. In this example, the heating control system calls for heat.

The MG used in determining CS can increase as DIFF increases. For example, if the DIFF is only 1 degree, then it may be most energy efficient to only call for a small amount of change to IT to begin to marginally warm the indoor space and thereby warm the wall cavities. Following this logic, MG can be 2, resulting in CS=IT+2. It can remain at that new set point until a further change in DIFF is seen. Taking this example further, if the outdoor temperature drops quickly and DIFF increases, for example, to 3, then determining a new CS with a larger margin can be prudent, such as an MG of 6, resulting in C=IT+6. Assuming the same TT of 38, a DIFF of 3 means an ET of 35 degrees, fairly close to freezing, so more aggressive adjustments to the calculated set point, i.e. larger MG, can be needed. Eventually, increases in CS and associated calls for heat from the heating system will increase IT enough to warm the indoor space, and thereby the wall cavity, and begin to decrease the DIFF.

EXAMPLE 2

Parameters:

TT=threshold temperature ET=equivalent wall cavity temperature

DIFF=TT−ET

DS=default set point (serves as default and minimum set point) MT=maximum allowable temperature FS=fail-safe set point IT=indoor temperature

If outdoor temperatures drop quickly for example, to 20 degrees F., IT=40, TT=38, and ET falls to 36, then the DIFF will rise to 2. Since ET<TT, the heating control system will signal the heating system to provide heat to the indoor space. IT will continue to rise until the ET=TT. Assuming the WT had reached equilibrium with respect to the outdoor temperature when the ET was determined to be 36, then an increase of about 4 or 5 degrees in IT can be expected to be adequate to bring ET up to 38. However, because of the lag in heat transferring from the indoor space to the wall cavity, the heat may run for a longer period than would otherwise be necessary.

In the case of extremely cold weather, outdoor temperatures may drop so low that the present invention can cause the IT to approach, for example, 55 degrees or more. Assuming the MT is set at 60 degrees, and outdoor temperature has reached zero degrees F., and then continues to drop, to −15 for example, ET can again drop, causing the system to call for heat. In this example, IT can increase to 60 degrees which equals MT. At that point, the heating control system will discontinue calling for heat from the heating system and allow the ET to remain below the TT. In this example, the heating control system can do one or more of the following: 1) display on the user interface that IT has reached the MT, 2) notify the user that the IT has reached the MT, 3) display on the user interface the DIFF, and or 4) notify the user of the DIFF. 

What is claimed is:
 1. A method for controlling a heating system, the method comprising: obtaining a reading for a temperature of a wall cavity in a structure served by a heating system which heats an indoor space adjacent to the wall cavity; determining an equivalent wall cavity temperature; when the equivalent wall cavity temperature is at or above a threshold temperature; selecting a chosen set point by selecting a default set point; when the equivalent wall cavity temperature is below the threshold temperature; determining a calculated set point based on the equivalent wall cavity temperature; comparing the calculated set point to the default set point and a maximum set point; selecting the chosen set point by selecting (1) the default set point if the calculated set point is below the default set point, (2) the calculated set point, if the calculated set point is between the default set point and the maximum set point, (3) the maximum set point, if the calculated set point is above the maximum set point; and; controlling the heating system to regulate the temperature of the indoor space according to the chosen set point.
 2. The method according to claim 1, wherein, when the calculated set point is above the maximum set point, a user is notified that the maximum set point is in use.
 3. The method according to claim 1, wherein, when the calculated set point is above the maximum set point, the user is notified of the equivalent wall cavity temperature and the difference between the threshold temperature and the equivalent wall cavity temperature.
 4. The method according to claim 1, wherein, when the equivalent wall cavity temperature is not able to be determined, a fail-safe set point is selected.
 5. The method according to claim 4, wherein, when the fail-safe set point is selected, the user is notified that the fail-safe set point is in use.
 6. A method for controlling a heating system, the method comprising: obtaining a reading for a temperature of a wall cavity in a structure served by a heating system which heats an indoor space adjacent to the wall cavity; obtaining a reading for an indoor temperature; determining an equivalent wall cavity temperature; when the equivalent wall cavity temperature is at or above a threshold temperature; selecting a chosen set point by selecting a default set point; when the equivalent wall cavity temperature is below the threshold temperature; comparing the indoor temperature to a maximum allowable temperature; and; controlling the heating system to increase the indoor temperature until the equivalent wall cavity temperature is at or above the threshold temperature, or until the indoor temperature is at or above the maximum allowable temperature.
 7. The method according to claim 6, wherein, when the indoor temperature reaches the maximum allowable temperature, the heat is no longer called for from the heating system.
 8. The method according to claim 7, wherein, when the indoor temperature reaches the maximum allowable temperature a user is notified that the indoor temperature has reached the maximum allowable temperature.
 9. The method according to claim 7, wherein, when the indoor temperature reaches the maximum allowable temperature the user is notified of the difference between the threshold temperature and the equivalent wall cavity temperature.
 10. The method according to claim 6, wherein, when the equivalent wall cavity temperature is not able to be determined, the system selects a fail-safe set point.
 11. The method according to claim 10, wherein, when the system selects a fail-safe set point, the user is notified that the fail-safe set point is in use.
 12. A heating control system comprising: at least one user interface; at least one computer programmed to: obtain a reading for a temperature of a wall cavity in a structure served by a heating system which heats an indoor space adjacent to the wall cavity; determine an equivalent wall cavity temperature; when the equivalent wall cavity temperature is at or above a threshold temperature; select a chosen set point by selecting a default set point; when the equivalent wall cavity temperature is below the threshold temperature; determine a calculated set point based on the equivalent wall cavity temperature; compare the calculated set point to the default set point and a maximum set point; select the chosen set point by selecting (1) the default set point if the calculated set point is below the default set point, (2) the calculated set point, if the calculated set point is between the default set point and the maximum set point, (3) the maximum set point, if the calculated set point is above the maximum set point; and; control the heating system to regulate the temperature of the indoor space according to the chosen set point.
 13. The heating control system according to claim 12, wherein, when the equivalent wall cavity temperature is not able to be determined, a fail-safe set point is selected.
 14. A heating control system comprising: at least one user interface; at least one computer programmed to: obtain a reading for a temperature of a wall cavity in a structure served by a heating system which heats an indoor space adjacent to the wall cavity; obtain a reading for an indoor temperature; determine an equivalent wall cavity temperature; when the equivalent wall cavity temperature is at or above a threshold temperature; select a chosen set point by selecting a default set point; when the equivalent wall cavity temperature is below the threshold temperature; compare the indoor temperature to a maximum allowable temperature; and; control the heating system to increase the indoor temperature until the equivalent wall cavity temperature is at or above the threshold temperature, or until the indoor temperature is at or above the maximum allowable temperature.
 15. The heating control system of claim 14, wherein, when the indoor temperature reaches the maximum allowable temperature, the method discontinues calling for heat from the heating system.
 16. The heating control system of claim 14, wherein, when the equivalent wall cavity temperature is not able to be determined, the system selects a fail-safe set point. 